Networker

[Networker] Is this a feature or bug?

2003-11-25 14:10:08
Subject: [Networker] Is this a feature or bug?
From: Craig Ruefenacht <Craig.Ruefenacht AT US.USANA DOT COM>
To: NETWORKER AT LISTMAIL.TEMPLE DOT EDU
Date: Tue, 25 Nov 2003 12:07:46 -0700
Howdy,

We noticed an interesting behavior after examining last night's backup run.
Below is a very small subset of the complete story, but it should be enough
to explain what we saw.  Our backup server is a HP-UX 11i on a K570 running
Networker 6.1.3 Build 428.

We have a filesystem on our Networker server that we backup.  Its entry in
/etc/fstab is as follows:

        /dev/vg05/lvol1 /t01 vxfs rw,suid,largefiles,delaylog,datainlog 0 2

Its a logical volume in a volume group and uses Veritas's filesystem on it.


In the saveset list for the Networker server, we list "/t01" as one of the
savesets to be backed up.

Occasionally, we unmount /t01 and remount it as /u01.  We do this manually,
i.e.

        umount /t01
        mount /dev/vg05/lvol1 /u01

The /etc/fstab does not change when we do this.  /etc/mnttab does change,
though, to reflect what is currently mounted.

When /dev/vg05/lvol1 is mounted as /u01, and Networker kicks off a backup,
we thought that Networker would try to backup /t01, and, since nothing is
mounted there and therefore /t01 is an empty directory, nothing would be
backed up.  What we saw last night was that even though /u01 was NOT listed
as a saveset for the Networker server, Networker somehow knew that what was
usually mounted under /t01 was now mounted under /u01, and so it backed up
/u01.  Here is a one-line snippet fro /nsr/logs/daemon.log showing this:

        11/25/03 06:00:18 nsrd: nsrserver:/u01 saving to pool 'Unix'
(C75680)

The relevant entry in /etc/mnttab for /u01 is

        /dev/vg05/lvol1 /u01 vxfs log,nodatainlog 0 0 1069713244

We are guessing that Networker looks in /etc/fstab for the filesystem /t01,
and then looks in /etc/mnttab to see if its mounted.  Since /t01 is not
mounted, Networker must then be looking for the device which should be
mounted as /t01 (looks in /etc/fstab again), and, upon finding the device
name, looks in /etc/mnttab to see where that device is mounted and then
proceeds to backup the path where the device is currently mounted,
regardless if that path is in the saveset list or not.  Is this logic
correct, or is Networker going about this differently?  It has to somehow
lookup the device and find the mount mount of that device....

We do not recall seeing this behavior in the past (both in Networker 6.1 and
our current version) when we've had the device that should be mounted under
/t01 actually mounted under /u01.  In the past, I believe that Networker
would go to /t01, and, finding an empty directory, not backup anything.  I
don't recall it backing up whatever path the device was mounted as - though
it very well could have been doing that and I simply wasn't paying attention
to it.

I don't know whether to call this a feature or a bug.  Usually its okay if
the filesystem on /dev/vg05/lvol1 gets backed up while it is mounted as
something other than /t01, but sometimes we don't want it backed up when we
do this.



--
Craig Ruefenacht
UNIX Administrator
USANA Health Sciences
http://www.usana.com

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